Electrical apparatus



' IQ H. SCLAT ER.

ELECTRICAL APPARATUS.

APPLICATION FILED JUNE I2, 1919.

Patented Oct. 18, 1921* I IvanH oe H.Sc| aL eT", @Mfi I His a lttorneg.

UNITEDSTATES PATENT OFFICE.

IVANHOE H. SCLATER, OF IITTSFIELD, MASSACHUSETTS, ASSIGITOR TO GENERALELECTRIC COMPANY, A CORPORATION OF YORK! ELECTRICAL APPARATUS.

Patented Oct. 18, 1921.

Application fi led me 12, 1919. serial No. 303,617.

T all whom it may concern Be it known that I, IvANHon I-I. SoLA'rER, acitizen of the United States, residing at- Pittsfield, in the county ofBerkshire, State of Massachusetts, have invented certain new and usefulImprovements in Electrical Apparatus, of which the following is aspecification.

My invention relates to cores for electrical apparatus, such astransformers, some reactors, and the like, and has for its generalobject an improved construction and method of effecting the same whichis economical and lends itself readily to manufacturing processes.

More specifically my invention relates to cores of the so calleddistributed type, or those in which the laminations are arranged ingroups, the groups being disposed in angular relation to one another toform a central leg for windings.

In coresof this type, it is customary to construct the groups ofL-punchings which are interleaved in alternate directions so that eachgroup comprises a generally rectangular body of punchings yielding a magnetic circuit having broken joints. In order that the central leg shallhave good magnetic properties and at the same time have an externalcontour yielding a relatively short mean copper turn, it is necessarythat, the sides of the lamination groups, intended to be associated toform such' central 'leg, should be designed'to coact to this end.

Heretofore a number of sizes of L-punchings for the core for apparatushaving a given rating was needed to effect this coac tion in ordertoproduce a group of laminations having a side whose configuration wasadapted to be dove-tailed into or interlocked with corresponding sidesof the other groups to produce the central leg; each rating having itsown set of sizes in L-punching's.

To provide this large variety of L-punchings for an extensive line ofdistributed core transformer and like electrical apparatus, adapted forvarying ratings and duties, en-

tailed a great outlay of money in material,

tools and equipment. It is hence one of the specific objects of myinvention to provide a core of this type suitable for such series ofsizes of transformers, etc, which is assembled from a minimum variety ofL-punchings.

To impose-a definite potential upon this type of core, its frame,clamps, and its tank or casing which incloses the apparatus embodyingthe core, it has been customary to ground all these parts; a conductorfor this purpose is therefore generally placed in among the corelaminations and brought out and connected to the frame and clamps. Thismode of making the ground connections, however, is tedious and somewhatexpensive. Accordingly it is still another object of my invention tosimplify this manner of making the ground connection, which isexpeditiously carried out by the arrangement of L-punching employed byme, since I merely bend out a portion of a free end of one of thelaminations to engage with the frame and clamps. Preferably, I provideone such ground connection for each group of laminations composing the'core, since it is desirable to insulate these groups from one anotherand from the frame to out down losses.

Still further objects and advantages of my invention will appear fromthe following detailed description whentaken in connection with theaccompanying drawing in which:

Figure 1 shows in perspective a view of a core constructed to embody myinvention. Fig. 2 is a top plan view of the core shown in Fig. 1. Figs.3 and 4 show respectively the type of L-punchings used in my invention;while Fig. 5 shows a cross-section of another form of central leg madefrom L- punchings in accordance with my invention.

Referring now to the drawings 10 indicates the assembled core made u yfitting together four groups of laminations 11, 12, 13 and 14 so as tomeet each other at right angles and form the central leg 15. The leg 15carries the windings 16 when assembled.

Each group of laminations is shown as having a stepped formation alongits inner side such as shown at the corresponding side of the othergroups. Two opposite groups, as 11 and 13, are so disposed that thereexists a groove, as at 18, in which the projecting step on an adjacentgroup 12 may be inserted in interlocking relation. In order to'build agroup of laminations having a side provided with a stepped formationsuch as will admit of this construction for the central leg, it isnecessary to provide amines??? hen ve y 17, where it abuts with disposedportions or legs, which are to compose such central core leg, shall beof differentwidths, as indicated at W and W in Figs. 3 and 4respectively where the leg W is one half the width of leg W.

The two sizes of Us here illustrated, comprise a set which is suflicientto build up the groups of laminations into the rectangular shapes hereshown in cotiperation with other similar Ls, as shown at M which areplaced to abut thereagainst. The horizontal portions or legs of these Lsare disposed some in the upper yoke and some in the lower yoke in apredetermined order, thus providing broken joints in the magneticcircuit. A set of more than the two sizes shown, however, will be usedwhere it is desired to construct a core capable of being assembled, orof receiving its windings in a preferred way.

Now in the design of electrical apparatus having magnetic cores, such asthe transformer shown in Fig. 1, it is customary to use sufficient ironin the core to bring the magnetic flux density up to a predeterminedvalue. Therefore for a line of transformers similar to that in'Fig.1,.each designed for a different rating, (2'. e., fora varying number ofampere-turns) the iron content of the core must be correspondinglyvaried, but instead of havin a set of punchings for each rating designedto give the proper iron content to the core, I make the one set of sizesstandard for all sizes in the series, and simply change the relativenumbers of certain of the laminations entering into each group so thatthecompleted cores for each rating will have the proper magnetic fluxdensity. The manner of effectin this will be more readily comprehendedfrom the following examples:

Suppose the transformer shown in Fig. l to have a rating of l50-KVA., acore group would be built up of suflicient punchings having wide legs asshown in Fig. 3 (such punchings enerally being .014 inch thick) until aheig t of 2.25 inches is reached, then punchings which have the narrowlegs would be added until a total height of 4.5 inches is reached. Foursuch groups would then be placed together so that their stepped sidesengage. In order that the groups should engage as indicated in Fig. 2 itis obviously necessary that the narrow leg W shown in Fig. 4 should bebut 225 inches in width and that the leg W should b'e4'.5 inches inwidth.

To build a transformer for a rating of 200 KVA., sufiicient wide-leggedpunchings would be used to build the group up .to aheight of 2.75inches, narrow-legged punchings being added until the total height is5.0 inches. When four such groups are assembled to form the core, thecentral leg would have a vertical ventilating duct passing axiallythrough it about 0.5 inch wide, as indlcated the section of such centralleg as continued, in this manner; the sides a and b of the cornernotches being kept with the same dimensions throughout. 4

To reduce eddy current losses in the central leg, I preferably insertfolded strips of insulation between the groups, which strips are bentover the edges of the laminations which are fitted together to form thecentral leg. These folded strips of insulation are inserted as indicatedby the black lines 24 in Fi 2 and as indicated at 25 in Fig. 5.

s hereinbefore indicated, a core OftlllS type constructed as abovedescribed, lends itself well to a construction affording a read ily madeground connection; the ground connection preventing the accumulation ofstatic or induced charges on the core. In

vmy improved construction the core lamina tions are electricallyconnected to the frame and the clamps, which are insulated from the corein order to increase the magnetic reluctance of this path to the leakageflux and thereby reduce eddy current losses. In Figs. 1 and 2, the freeend of each narrow leg WV adjacent the central core'leg is shown as bentout at 20 and the strip of insulation 21 for insulating the core fromthe clamps, inserted behind it. These strips of insulation 21 arecustomarily laid along the yoke portions of each group of laminationsand held in place by. the clamping angles 22. The clamps are heldtogether for clamping the core members in place by means of bolts 23,the insulating qualities of the paint or varnish applied to the boltsand clamps being suflicient to keep the local circulating current,induced there- .in down to a negligible value.-

' aving now described what is at present the best means known to me forcarrying out an embodiment of my invention, I- would have it understoodthat such means are merely illustrative and that I- donot mean to belimited thereby to: the exact details shown nor in the choice-ofrecognizedequivalents except as defined in my claims hereunto appended.1

What I claim as new and desire to secure by Letters Patent ofthe UnitedStates,is

1. The method of constructing distributed cores with four outer legs fora line, of electrical apparatus rated for varying duties and havinginterlocking groups of laminations arranged to have the r 0011supporting 'one portion of such group being varied in dimensions tocorrespond with the ratings desired. I l

2. The method of constructing distributed cores with four outer legs fora line of electrical apparatus rated for varying duties and havinginterlocking groups of laminations arranged to have their coilsupporting edges lying on a circle, which consists in making a fewstandard sizes of L-punchings, assembling some of each sized punching-sin groups a portion of such groups being varied in thickness tocorrespond with ratings to be given, arranging the punchings in saidgroups to form a complete magnetic circuit having broken joints, andfitting each group with another group at one edge and at angles of 90 toeach other. I i

3. The method of constructing distributed cores with four "outer legsfor a line of electrical apparatus ra ed .for varying duties and havinginterlockeu groups of laminations arranged to have their coil supportingedges lying on a circle, which consists inmaking a few standard sizes ofL-punchings, assembling some of each sized punching into stepped groupsadapted for dovetailed engagement with other groups disposed at rightangles therewith, and varying the number of. punchings composing apredetermined step of each group in amounts varying with the ratingdesired whereby the distances from the corners of the central leg wheresaid groups meet to their winding supporting edges are maintainedmutually equal.

4. In electrical apparatus, the combinaangularly disposed roups oflaminations composed of L-puncfiings, clamping members embracing theyokes of the assembled core, and strips of insulation inserted betweensaid members and the core; the free end of ,a lamination of a groupbeing bent out from under said insulation and placed in conductingrelation with one of said clamping members.

5. In electrical apparatus, the combination with awind'lng, of a coremade from angularly disposed groups of laminations composed ofL-punchings, strips of insulation laid over the abutting edges of saidgroups, clamping membersembracing the yokes of the assembled core, andother strips of insulation inserted between saidmembers and the core;the free end of an external lamination of the core being bent out fromunder the last named insulation and placedin conducting relation withone of said clamping members.

6. In electrical apparatus, the combination with a winding, of a corecomposed of laminated punchings, a clamp for holding the core inassembled relation and insulating material inserted between said coreand said clamp; a portion of one of the laminations being bent out fromunder the insulating material and placed in conducting relation withsaid clamp.

In witness whereof, I have hereunto set my hand this 9th day of June,1919.

IVANHOE H. 'SGLATER.

tion with a winding, of a core made from

